1. Field of the Invention
The present invention relates to a photographing optical system and more particularly, to a compact photographing optical system used in portable electronics.
2. Description of the Prior Art
In recent years, with the popularity of portable electronics, the demand for compact imaging lenses is increasing, and the sensor of a general photographing camera is none other than CCD (charge coupled device) or CMOS Sensor (Complementary Metal Oxide Semiconductor Sensor). Furthermore, advanced semiconductor manufacturing technology has allowed the pixel size of sensors to be reduced and electronic products have become more compact and powerful, there is an increasing demand for compact imaging lenses featuring better image quality.
A conventional compact photographing optical system, in order to reduce manufacturing costs, is usually composed of a two-lens structure, such as a two-lens imaging lens assembly disclosed by U.S. Pat. No. 7,525,741. However, two-lens structure has limited ability in correcting aberrations, which is unable to satisfy the demand of high level imaging modules. On the other hand, utilizing too many lens elements in the assembly will also be difficult for the total track length of the lens assembly to stay compact.
To obtain high image quality while maintaining the compact feature of the lens assembly, photographing optical system with three lens elements proves to be the solution. U.S. Pat. No. 7,564,635 discloses a photographing optical system with three lens elements. However, three lens elements of the lens assembly are all positive refractive lens elements, which make it difficult to correct the aberration (such as chromatic aberration) in the system and the image quality is compensated.
Therefore, a need exists in the art for a photographing optical system that features high image quality without having a long total track length and applicable in portable electronic products.